Aims: To evaluate the potential risks of dental treatment during pregnancy and effects on childhood development.Accomplishments: We originally had looked at the relationship between fish consumption, dental treatment during pregnancy and number of amalgams fillings in a woman's mouth and her umbilical cord mercury levels. We subsequently recognized that the cords had been analyzed by two different machines and there was something wrong with the measurement. We had hoped that the laboratory that did the measurements could straighten out the problem but they apparently lost the key laboratory books containing data on how their methods measured against a known standard. We therefore have abandoned using the biological measure unless the laboratory can rectify the situation and use questionnaire data instead.